# 2016q3 Homework1 (compute-pi)
contributed by <`Quexint`>

## 開發記錄

### `v0` 原始版本

### `v1` 支援 `make plot`

### `v2` 加入 Error Rate 及 重推公式

- 參考
- https://hackpad.com/Hw1-Extcompute_pi-geXUeYjdv1I

- 改寫 `baseline`, `OMP2`, `OMP4` 成 `baseline_plus`, `OMP2P`, `OMP4P`
hh

double compute_pi_baseline(size_t N)
{
    double pi = 0.0;
    double dt = 1.0 / N;                // dt = (b-a)/N, b = 1, a = 0
    for (size_t i = 0; i < N; i++) {
        double x = (double) i / N;      // x = ti = a+(b-a)*i/N = i/N
        pi += dt / (1.0 + x * x);       // integrate 1/(1+x^2), i = 0....N
    }
    return pi * 4.0;
}
double compute_pi_baseline_plus(size_t N)
{
    double pi = 0.0;
    for (size_t i = 0; i < N; i++) {
        double x = N * N + i * i;
        pi += N / (x);
    }
    return pi * 4.0;
}

- 時間下降一半以上，精準度不變